Electromagnetically coupled patch antennas have been long known in the art. In this technical field, a parasite resonant element and an exciting element (exciter) combine to produce the desired transmission and reception functions. FIG. 1 shows a prior art proximity coupled antenna 10. The exciting element 11 is located at a ground surface and is connected to a signal source via a connector. A radiating element or parasitic element 12 is spaced at distance above the exciter 11. Exciter 11 is secured to the surface of the ground plane 13 function as a primary and secondary transformer adapted to act as a doubly tuned circuit.
Electromagnetically coupled patch antennas can be used in general broadband broadcast and reception with high gain. However, the secondary element 12 must be elevated above the ground plane 13 and must not share any effective connection. It is difficult to maintain a required separation distance in environments where severe physical vibration or shock will affect the antenna.
U.S. Pat. Nos. 5,400,040 and 5,337,066 disclose patch antenna structures where all elements are substantially located upon a single planar surface to accommodate use in environmentally difficult locations. U.S. Pat. Nos. 4,907,006 and 5,200,756 disclose a parasitic element which descends to the level of a ground plane. U.S. Pat. No. 5,929,812 discloses parasitic elements short circuited to a ground plane. While the prior art contains certain disparate attempts to provide a rugged patch antenna, such prior art patch antennas are still constructed in a manner in which vibration and shock will tend to cause decreased performance over time.
There is a need for an antenna with identical or superior performance for placement in severe environments without adverse effects.